Stug III was one of a series of assault guns/tank destroyers produced by the Germans during the war. Assault guns were easier, cheaper and less time consuming to produce than turreted tanks and that is why German factories built them in large numbers. Cost of single Ausf G was 82500RM making it cheaper than both PzKpfw III Ausf M at 103163RM and PzKpfw IV Ausf F2 at 115962RM. It is interesting to see that almost four Ausf Gs could be purchased for the cost of single King Tiger.
In 1935, Colonel Erich von Manstein proposed that Sturmartillerie units were to be formed and used for direct support of infantry divisions. They were to be equipped with assault guns mounted on tracked chassis. Used to accompany the infantry into the attack, the assault gun's main aim was to knock out pill-boxes, machine gun nests, anti-tank guns and other obstacles.
On June 15 1936, the order was given to Daimler-Benz AG to develop and produce an armored infantry support vehicle mounting 75mm gun. The gun was to have a limited traverse of minimum 25 degrees in order to provide direct support up to 6 kilometres. The gun was to be mounted in a superstructure that provided full protection for the crew. The height of this vehicle was not to exceed the height of an average man. Daimler-Benz AG being already involved in the development and production of Panzerkampfwagen III tank decided to use its chassis and components for this new vehicle. The experimental "0" series of five prototypes (chassis number 60201 to 60215) was produced in 1937 by Daimler-Benz - Pz.Sfl.III (s.Pak). Prototypes were pre-production Panzerkampfwagen III Ausf B tanks mounted with mild-steel superstructures housing short-barrelled 75mm StuK (Sturmkanone) gun designed and produced by Krupp. Vehicles were extensively tested at Kummersdorf, Doberitz and other testing / training facilities e.g. Jueterbog. Prototypes remained in use as training vehicles as late as 1942.
First production vehicles based on Panzerkampfwagen III Ausf F chassis and components, entered production in 1940. The 75mm StuK 37 L/24 gun was mounted offset to the right in a sloped superstructure. Superstructure was made of armor plates and was mounted on the welded hull. Side hull escape hatches present in the original Panzerkampfwagen III Ausf F hull were removed and frontal hull armor protection was increased from 30mm to 50mm. From January to May of 1940, 30 Sturmgeschutz III Ausf A were produced by Alkett.
First 24 Stug III Ausf A assault gun out 30 produced equipped Sturmartillerie Batteries 640, 659, 660 and 665 and first saw service during the French Campaign. Each battery according to organization scheme from November of 1939 had 6 assault guns in three platoons (with 2 assault guns each). Sturmartillerie Battery 640 became organic to Infantry Regiment Grossdeutschland and was renamed to 16th Sturmartillerie. Last 6 assault guns were issued to SS Sturmartillerie battery of Leibstandarte SS Adolf Hitler division. Two more batteries were formed - 666th and 667th but didn't see combat in France.
In August of 1940, Sturmartillerie units were reorganized into Abteilungen (battalions) with 18 assault guns in three batteries (with 6 assault guns each). In early 1941, the battalions were renamed - Sturmgeschuetz Abteilungen and batteries to Sturmgeschuetz Batteries. In March/April of 1941, all Sturmgeschuetz Batteries had the number of assault guns increased to seven. In 1942, with the introduction of long-barrelled Stug III (75mm L/43 and L/48), Sturmgeschuetz Abteilungen were reformed and number of assault guns was increased to 28 per battalion. Each battalion still had three batteries but number of assault guns in platoons was increased to three. In November of 1942, Sturmgeschuetz Abteilungen were reformed again and number of assault guns was increased to 31 per battalion with three additional assault guns for battery commanders. This type of organization often referred to as Sturmgeschuetz Brigade remained in use until the end of the war. In June of 1944, new organization scheme was introduced - Sturmartillerie Brigade with 45 assault guns, including 33 Stug III/IV (75mm L/48) assault guns and 12 Sturmhaubitze 42 (105mm L/28) assault howitzers. Brigade had three batteries with 2 Stug IIIs for each battery command, while each battery had two platoons of four Stug IIIs and one of four StuH 42s. This organization scheme was used alongside the Sturmgeschuetz Brigade scheme to the end of the war. In practice, these ideals were hardly ever achieved and then only highly favoured formations received the full complement.
Towards the end of the war, Stugs (40) were often issued to other units as replacement for tank destroyers and even tanks. Since 1944, Stug III (40) were also used as replacements for PzKpfw III, PzKpfw IV and even PzKpfw V Panther in Panzer Abteilungs. That practice was a mistake, but the desperate situation and the overall shortage of tanks made it a necessity. During the course of war, Stug III assault guns were issued to Sturmartillerie Batteries, Sturmgeschuetz Abteilungen, Sturmgeschuetz Brigades, Sturmartillerie Brigades, Ersatz (Reserve) Abteilungen and Funklenk (Remote Control) Companies. Stug III assault guns served on all fronts of WWII to the end of the war. Only, elite Wehrmacht (e.g. Grossdeutschland) and Waffen SS (eg. LSSAH, Das Reich, Totenkopf) divisions had Sturmgeschutzbrigaden as permanent part of their divisions.
Sturmgeschutz III was originally designed as an assault weapon, but as war progressed it became more of a defensive one. It evolved into an assault gun and tank destroyer in one. Its main role was to providing anti-tank support to the units in its area of operation.
Ausf A was followed by improved Ausf B, C, D and E, all armed with short 75mm StuK 37 L/24 gun. All versions featured number of modifications specific to vehicles that followed them in production. Last Ausf E was produced in March of 1942. Total of 822 Ausf A, B, C, D and Es was produced by Alkett and their official designation was Gepanzerter Selbstfahrlafette fur Sturmgeschutz 7.5cm Kanone Ausf A-E / Sd.Kfz.142. Early Stugs remained in active service until mid 1943. Many Early models were recalled to the factory to be rearmed with newer guns and up-armored by addition of armor plates. Some older variants returned for repairs were often re-equipped with parts from newer variants creating completely non-standard variants (e.g. Stug III Ausf C armed with 75mm StuK 40 L/48 gun in Saukopf mantlet destroyed at Altdamm, 1945 and Stug III Ausf E armed with 75mm StuK 40 gun destroyed in Berlin, May 1945).
Stug III Ausf E was the first of the series to be provided with 7.92mm MG34, which was carried inside the superstructure for local defense.
Three Ausf D vehicles were send to North Africa and saw service with Sonderverband z.b.V 288 - special deployment unit.
In March of 1942, Ausf F entered production. It was not only an assault gun but also a badly needed tank destroyer. Early models were mounted with long 75mm StuK 40 L/43 and late models (31) with longer L/48 gun. It was produced until September 1942 with 359(360) produced. Ausf F was then replaced by Ausf F/8 armed exclusively with L/48 gun. It was produced until December of 1942 with 334 produced. Ausf F/8 paved the way for final Sturmgeschutz III model - Ausf G. Stug III Ausf F, F/8 and G's were also called Stug III (40), because they were all armed with 75mm StuK 40 guns. Stug III Ausf F and Ausf F/8 were produced by Alkett and their official designation was Gepanzerter Selbstfahrlafette fur Sturmgeschutz 7.5cm Sturmkanone 40 Ausf F-F/8 / Sd.Kfz.142/1
In order to improve Stug III's performance, in 1942, small number of various Stug III models (from Ausf B to Ausf F) was rearmed with 75mm Stuk L/33 guns, which externally resembled 105mm StuH 42 L/28 howitzers causing confusion. In reality Sturmgeschutz was never armed with this of gun. 75mm Stuk L/33 gun was invented by the British, who misinterpreted German photos of Stug III Ausf F with its longer L/43 gun, which had the muzzle break painted out by censors as new type of gun - L/33.
In May and June of 1943, 10 of retired and battle damaged Stug III Ausf F/8 were converted into flame-thrower tanks armed with 14mm Flammenwerfer. They were designated as Sturmgeschutz III (Fl). From June of 1943 to January of 1944, all Sturmgeschutz III (Fl) were used for training in Germany, while from January to April of 1944 all were rearmed with 75mm StuK 40 L/48 guns.
Ausf G entered production in December of 1942 and remained in production until March/April of 1945. It was the most numerous from all Sturmgeschutz III guns and some 7893 were produced by Alkett (Altmaerkische Kettenfabrik GmbH) and MIAG (Muehlenbau-und-Industrie AG). Production reached its peak when in 1944, 4013 Ausf Gs left factories. Alkett produced over 5000 Ausf, while MIAG began production in March of 1943 and produced some 3000 vehicles. Production numbers include 165 PzKpfw III Ausf M chassis used to produce Ausf Gs in 1943 and 173 PzKpfw III Ausf Ms converted to Ausf Gs by Alkett and MIAG in 1944. Ausf G was produced in four production series - chassis numbers 76101 to 77550, 91751 to 94250, 95001 to unknown and 105001 to unknown.
Ausf G used Ausf F/8's hull, suspension, engine and other components, while superstructure was modified. Superstructure was widened, its 30mm sides were sloped at 79 degrees, the roof was raised in the rear and its rear 30mm superstructure wall was mounted at 90 degrees. This provided more room for both the commander and loader.
The other changes included the layout of the roof, addition of commander's cupola with seven periscopes (each could be moved up or down) and sighting flap for binocular spotting telescope along with a 10mm machine gun shield in front of loader's hatch (from December of 1942 to April of 1944). Early vehicles had movable cupola (until October of 1943), mid vehicles had it mounted in a fixed position (until October of 1944) and late vehicles again had movable cupola with additional protective cover. Also, early vehicles had 50mm frontal hull armor increased to 80mm by addition of 30mm bolted armor plate, while vehicles produced since May of 1943 by Alkett and since October of 1943 by MIAG had 80mm frontal hull armor. Early models were also mounted with KFF2 (Kampfwagen Fahrer Fernrohr) driver's episcopes.
During the production, modifications were made to Ausf G. They included introduction of 80mm cast Saukopf (also known as Topfblende) mantlet in February of 1944; the coaxial MG in early 1944, installation of Nahverteidigungswaffe (90mm NbK 39 close-in defense weapon) and roof mounted remote controlled MG (Rundum Feuer) in late spring of 1944. In addition, vehicles produced since January of 1943 had the fighting compartment fan mounted on the rear superstructure wall instead of the roof. Two kinds of "Saukopf" mantlet were produced and mounted on Stug III Ausf G, one housing only the gun and other housing the gun and coaxial machine gun (from September of 1944). Original "boxy" gun mantlet was made of 50mm (front) and 30mm (sides) armor plates. Ausf Gs were also mounted with 5mm Schurzen since mid 1943.
Stug III Ausf F, F/8 and G's were also called Stug 40 Ausf F, F/8 and G, because they were all armed with 75mm StuK 40 guns. Those last three models performed the role of tank destroyers rather than that of assault guns.
On August 1st of 1940, it was planned to convert 12 Sturmgeschutz IIIs into submersible assault guns in preparations for the Invasion of England (Operation Sealion) but conversion never took place.
From April to June of 1943, some 61 Stugs were assigned to Panzerkompanien (Funklenk) as command vehicles for SdKfz.301 (Schwere Ladungstrager Ausf A/B/C - Borgward) tracked demolition charge layers, which were radio-controlled.
Sturmgeschutz III's design underwent many changes including various modifications made to the suspension (e.g. sprocket and idler design), superstructure (e.g. headlights, shape, size, ventilator, cupola) and other equipment (e.g. sight, remote control machine gun). Each variant featured some modifications to the overall design, creating the visible difference between Ausf B and Ausf G. All Stug IIIs were operated by the four men crew - commander, gunner, loader / radio operator and driver.
Very common field practice was the addition of a layer of concrete added over the armor plate above the driver's position to improve the protection. Since mid 1943, Stug IIIs were also equipped with Schurzen (armor skirts) for further protection. Also many earlier version were recalled to the factory to be rearmed with never guns and up-armored by addition of armor plates. Number of vehicles was also mounted with additional armor plates during their service by field workshops. Some older variants returned for repairs were often re-equipped with parts from newer variants creating completely non-standard variants. Models produced between September of 1943 and September of 1944, were factory applied with Zimmerit (anti-magnetic paste) with "waffle plate" or standard design. At the same time, many Stug IIIs already in service were also applied with Zimmerit. Very common were the canister/storage racks or steel rails mounted on the engine compartment.
Overall, Sturmgeschutz series proved to be very successful, and served on all fronts as assault guns and tank destroyers in both offensive and defensive mode. Sturmgeschutz III with its low silhouette was a difficult target and a dangerous opponent. Sturmgeschutz crews were considered to be the elite of the artillery units and were issued special field grey (version of panzer) uniforms. Sturmgeschutz units held very impressive record of tank kills some 20000 enemy tanks by spring of 1944. As of April 10th of 1945, there were 1053 Stug IIIs and 277 StuH IIIs in service. Approximately 9500 Sturmgeschutz IIIs of various types were produced until March of 1945 by Alkett and small number by MIAG.